These results incited us to revisit the emission of the HCN and HNC isotopologues in L1157-B1 in a more comprehensive and accurate way than was possible before. This study benefits from the unbiased and high-sensitivity millimeter spectral line survey of the shock region carried out as part of the IRAM 30m Large Program ASAI ("Astrochemical Surveys At IRAM", [1]}). In order to better understand and constrain more precisely the impact of the shock on the chemistry of HCN and HNC, we have also investigated the properties of their isotopologue emission in the envelope of the Class 0 protostar L1157-mm, at about 1 arcmin away, which we took as a proxy of the initial gas composition before the arrival of the shock. The origin of the molecular emission was then derived from comparison of our observational results with the predictions of the time-dependent gas-grain chemical and shock model UCLCHEM [2]}.
